1. Field of the Invention
This invention relates generally to the air bag system which is increasingly employed in various cars to improve safety at the time of a car crash. More particularly, the present invention relates to a mounting structure of an air bag module for a vehicle front passenger seat.
2. Description of the Prior Art
As is well known, the air bag system is a safety device incorporated in a car for preventing the driver and/or front passenger from impinging directly onto front interior parts (the steering wheel and the instrument panel) at the time of a car crash, thereby eliminating or reducing the human injury or death. Indeed, this system is known to compensate for what is lacking in the known safety belt system.
In general, the air bag system mainly comprises a plurality of shock sensors, a controller for generating an actuation signal when one or more of the shock sensors have detected a true crash, a gas generator (inflator) for explosively generating nitrogen gas in response to the actuation signal, and an air bag connected to the gas generator for expanding toward the driving seat or front passenger seat at the moment of the crash. The shock sensors are arranged at different portions of the car body such as the bumper and fenders suitable for detecting a car crash, whereas the controller is typically disposed on the front bulkhead
On the other hand, the gas generator and the air bag constitute a single housed unit called "air bag module" together with other related components. The air bag module is normally arranged in a central portion of the steering wheel in the case of the driving seat air bag system or within the instrument panel in the case of the front passenger seat air bag system.
The air bag module for the front passenger seat is typically supported on a cross member called "pillar-to-pillar member" which extends widthwise of the car within the instrument panel, as disclosed in Japanese Patent Application Laid-open Nos. 2-303948 and 2-303952 for example. The pillar-to-pillar member is a structural part which is used for supporting the instrument panel and the steering wheel.
In either of the above laid-open Japanese patent applications, the air bag module is supported above the pillar-to-pillar member at a position corresponding to the glove box (glove compartment) because the glove box is normally arranged in front of the front passenger seat. Thus, in order to provide a sufficient mounting space for the air bag module, it is necessary to downwardly displace the pillar-to-pillar member from a normal vertical position which is the position of the pillar-to-pillar member when no air bag module is provided.
However, if the pillar-to-pillar member is downwardly displaced, it approaches the glove box and the knees of the driver and front passenger. As a result, the glove box and the instrument panel are mechanically reinforced at portions thereof near the knees of the driver and front passenger by the thus lowered pillar-to-pillar member. Therefore, when the knees of the driver and front passenger impinge on the instrument panel and the glove box at the time of a car crash, a large crash load is applied to the knees, which may result in a serious injury.
Further, the downward displacement of the pillar-to-pillar member inevitably leads to a reduction of the glove box volume. Additionally, if the glove box has no ceiling of its own, the lowered pillar-to-pillar member becomes visible from inside the cabin when the glove box is opened, thus deteriorating the appearance.